Process for the manufacture of composite filaments and yarns

ABSTRACT

Composite filaments and yarns having excellent spinnability, dyeability and crimp developing properties, and exhibiting improved properties such as a small bulk density after development of crimps, a lower number of breakages in the monofilament or yarn during spinning, reduced deep dyeing defects, improved natural draw ratio, and development of fine, uniform helical crimps are obtained by melt-spinning component (A) a mixture, preferably having Mw/Mn of more than 2.5 selected from (i) mixtures obtained by continuously mixing an end product in the molten state obtained by a multi-step continuous polycondensation reaction with at least one intermediate product in the molten state occurring in this polycondensation reaction system, and (ii) mixtures obtained by continuously mixing at least two of said intermediate products, and component (B) at least one polymer having a viscosity different from that of component (A).

' United States Patent [none 51 June 20, 1972 [72] Inventor: Takeshi lnoue, Kurashiki, Okayama Prefecture, Japan Kurashiki Rayon Co., Ltd., Okayama Prefecture, Japan 221 Filed: July 25,1969

21 App1.No.: 844,910

[73] Assignee:

[30] Foreign Application Priority Data July 27, 1968 Japan ..43/53241 [52] U.S. Cl ..264/171, 161/173, 260/75, 260/78, 264/168 [51] Int. Cl. ..B29f 3/10 [58] Field ofSearch ..161/173, 175, 177; 264/171, 264/174, 168; 260/75, 78

[56] References Cited UNITED STATES PATENTS 2,439,815 4/1948 Sisson ..28/82 2,861,319 11/1958 Breen ..161/178 3,209,402 10/1965 Riley et al.. .264/D1G. 19 3,399,259 8/1968 Brayford ..161/173 3,408,277 10/1968 Martin et a1. ....264/168 3,408,433 10/1968 Brayford ..264/11 (EG) (CAT) (DMT) 3,447,583 6/1969 Herrmann et al. ..260/78 L 3,459,846 8/1969 Matsui et al. ..264/171 3,472,829 10/1969 Claybaugh et al ...260/93.7 3,533,904 lO/l970 Jurkiewitsch ..161/177 X FOREIGN PATENTS OR APPLICATIONS 41/21932 12/1966 Japan 264/DlG. l9 43/13352 6/1968 Japan..... ....264/DIG. l9 43/21504 9/1968 Japan ..264/DIG. 19

Primary E.\'aminerJay H. Woo Atrorney--Sherman and Shalloway [5 7] ABSTRACT Composite filaments and yarns having excellent spinnability', dyeability and crimp developing properties, and exhibiting improved properties such as a small bulk density after development of crimps, a lower number of breakages in the monofilament or yarn during spinning, reduced deep dyeing defects, improved natural draw ratio, and development of fine, uniform helical crimps are obtained by melt-spinning component (A) a mixture, preferably having Mw/Mn of more than 2.5 selected from (i) mixtures obtained by continuously mixing an end product in the molten state obtained by a multi-step continuous polycondensation reaction with at least one intermediate product in the molten state occurring in this polycondensation reaction system, and (ii) mixtures obtained by continuously mixing at least two of said intermediate products, andcomponent (B) at least one polymer having a viscosity different from that of component (A).

7 Claims, 10 Drawing Figures (POLYESTER B) (POLYESTER A) PATENTEDmzomz 3,671,620

' SHEET 10F 5 (E6) (CAT) (POLYETER B) (EG) (CAT) J (DMT) 2' g '6! (EMT) I I0 I (POLYESTER A) PATENTEDJUM201972 3 671 620 SHEET 2 OF 5 (EG) (cm 2 3 Mr H (o J 7 H F/g3 2r e 5 w-l &--4

(WATER) (NYL (STABLIZER) SALT 4 (POLYAMIDE B) (POLYAMIDE A) (SWATER TABLIZER)? (POLYAMDE B) (POLYAMDE A) (E6) (CAT) Fl? 6 DMT D H I (POLYESTER A) (POLYESTER B) PATENTEfiJunzo I972 3,671,620

SHEET u or 5 F/g- 7 (E6) (CAT) (DMT) l I2 2-40 I (POLYESTER A) (POLYESTER P'ATE'N'TEnJunzo 1912 3,671,820

SHEET 5 UF 5 H 9 ha 9 (WATE SALT 5 (POLYAMIDE A) (POLYAMIDE B) (POLYAMIDE A) (POLYAMIDE B) A,

PROCESS FOR THE MANUFACTURE OF COMPOSITE FILAMENTS AND YARNS This invention relates to a process for the production of composite filaments and yarns of excellent quality at low cost. The composite filaments and yarns obtained have crimpability, are excellent in spinnability, dyeability and crimp developing properties, and exhibit improved properties such as a small bulk density after development of crimps, a lower number of breakages in the monofilament or yarn during spinning, reduced deep dyeing defects, improved natural draw ratio, and development of fine, uniform helical crimps. More particularly, the invention relates to a process for the production of composite filaments and yarns containing them by meltspinning simultaneously at least two components of a linear polycondensation product of different melt viscosities through a spinneret, characterized by melt-spinning component (A) which is a mixture, preferably having W/m of more than 2.5 selected form (i mixtures obtained by continuously mixing an end product in the molten state obtained by a multistep continuous polycondensation reaction with at least one intermediate product in the molten state occurring in this polycondensation reaction system, and (ii) mixtures obtained by continuously mixing at least two of the intermediate products, and component (B) which is at least one polymer having a viscosity different from that of component (A), preferably at least one polycondensation product having such different viscosity.

Heretofore, it has been known that at least two linear polycondensation products having different viscosities but the same composition could be spun to form filaments having crimpability or crimp bulkiness. The greatest disadvantage of this method is that a plurality of polycondensation apparatus are necessary to produce the component polymers. This involves the necessity of using a small-sized polycondensation vessel and results in a high cost of construction.

it would of course be possible to operate only one polycondensation vessel so as to obtain a polycondensate of a high viscosity and a polycondensate of a low viscosity alternately and store them in a granule form. However, the amount of the granular material to be stored increases greatly, and large amounts of polycondensates having viscosities intermediate between the intended high viscosity polycondensates and the low viscosity polycondensates are fonned. Moreover, it is very difficult to mix solid granules uniformly. Since the spinning condition in the preparation of composite filaments is very subtle, the incorporation of the materials having an intermediate viscosity adversely affects the spinning conditions, and therefore, some measure becomes necessary to do away with the polycondensates having a intermediate viscosity.

It is very easy to carry out a polycondensation reaction batchwise, but the resultant polycondensate has a nonuniform quality as compared with those obtained by the continuous process and has bad reproducibility of quality. Hence, such polycondensates is inferior to those obtained by the continuous process as a material for preparation of composite filaments. For this reason, the yield in the spinning process is low, and the occurrence of fuzzes and the irregularity of dyeing are frequently seen in the final products.

In the present invention, polycondensation reaction products obtained from a multi-step continuous polycondensation system are used as one component. Specifically, the above-mentioned mixture (i) or (ii) is taken out from a single apparatus for a multi-step continuous polycondensation and employed as one component (A) of the composite filaments or yarns. It is subjected to conjugate-spinning together with at least one polymer as component (B) having a different viscosity from that of the component (A), preferably component (B) is another polycondensation reaction product obtained from the above-mentioned multi-step continuous polycondensation reaction system.

There are many reasons why no attempt has heretofore been made to take out the above-mentioned mixture (i) or (ii) from a single continuous polycondensation system and using it as one component of composite filaments or yarns. In any case, a plurality of polycondensation apparatus have been used heretofore. Among the above-mentioned reasons are 1. Under the continuous polycondensation reaction conditions, there is, depending upon the temperature or pressure conditions, a limit in the number of places from which intermediate products can be withdrawn, and therefore, it is difficult to withdraw intermediate products of the desired viscosities.

2. Incident to the withdrawal of the intermediate products, fluctuations or disorders occur in the polycondensation conditions to a lesser or greater extent. It is, however, practically impossible to control the polycondensation condutions in response to such fluctuations or disorders, and consequently, it becomes difficult to control the viscosities.

3. It is practically impossible to connect a spinning step directly with the polycondensation step, which direct spinning being a great advantage in continuous polycondensation.

It has now been found that when intermediate products in a multi-step continuous polycondensation reaction are withdrawn not directly from the reaction zones, but from passages or zones for transfer of intermediate products which connect the multi-staged reaction zones, no such disadvantages as mentioned above occur and it is possible to take out mixtures such as (i) and (ii) mentioned above advantageously both with respect to operation and equipment, and that by using such mixture as one component, it is possible to produce with good reproducibility composite filaments which have crimpability, are excellent in spinnability, dyeability and crimp developing properties, and exhibit improved properties such as a small bulk density after development of crimps, a lower number of breakages in the monofilament or yarn during spinning, reduced deep dyeing defects, improved natural draw ratio and development of fine, uniform helical crimps.

Accordingly, an object of the invention is to provide a process for the production of composite filaments and yarns having the above-mentioned advantages.

Many other objects and advantages of the invention will become apparent from the following description.

In the present invention, it is essential to use a mixture selected from the group consisting of (i) and (ii) as one component (A) of the composite filaments or yarns. The other component (B) may be any polymer having a viscosity different from that of the component (A). it may be a polymer produced by a different polycondensation reaction, or it may be a polymer of different kind. Preferably, it is a linear polycondensation product, and advantageously, it is one obtained from the same multi-step continuous polycondensation process from which component (A) is obtained.

The component (A) used in the invention is a mixture selected from i. mixtures obtained by continuously mixing an end product in the molten state obtained by a multistep continuous polycondensation reaction with at least one intermediate product in the molten state occurring in the same polycondensation reaction system, and

ii. mixtures obtained by continuously mixing at least two of such intermediate products. The state of mixing in these mixtures can be determined by measuring the molecular weight distribution. If the state of mixing is extremely non-uniform, the molecular weight distribution of the mixture is merely a distribution obtained by combining the molecular weight distributions of the respective components according to the mixing ratio. On the other hand, if the state of mixing is good enough and there is a sufficient time lapse after the mixing, the distribution approaches that of a single polycondensate of the same viscosity. It appears that the excellent quality of the v composite filaments and yarns of the invention is seen when the state of mixing is intermediate between these two extreme cases.

As an index for expressing the mo lecular weight distribution in a simple manner, a value (W/Mn) obtained by dividing a weight average molecular weight (W) with a number average molecular weight (Dean be conveniently used. A straight-chain polycondensate obtained by polycondensation in a molten state theoretically has an Wm value of 2.0, and actually usually 1.7 to 2.5.

. most preferably 0.8 x mi/176x3 0.4 W Wi 0.3 x WnTmcaL 1.4. [f the (MW/Mn) values of the mixtures are within this range, the spinning of the mixture as one component of the composite filament can be effected in good condition as compared with the preparation of composite filaments from a single polycondensate having the same viscosity. The composite filaments and yarns obtained have reduced dyeing deficiencies, and have an excellent ability to develop crimps.

It is not entirely clear why the use of the mixture (i) or (ii) mentioned above as component (A) is necessary in the process of this invention to obtain composite filaments or yarns of good quality. But as will be shown in Tables l and 2 appearing later in the specification, the objects of the invention cannot be achieved even if a polymer is used whose viscosity has been reduced identical with that of the mixture employed in the present invention by using two polymerization apparatus or by storing a part of the polymer prepared in the same apparatus.

The polycondensates usable as component (A) in the present invention are linear polyamides, linear polyesters and linearpolyureas. These polycondensates are usually obtained by continuous polycondensation in two or more steps. The preparation of the mixtures (i) or (ii) mentioned above is effected continuously while the polycondensates are still in-a molten state immediately after withdrawal from a continuous multi-step polycondensation system. Any mixing device can be used which does not cause, stagnation within the device, and which does not necessitate an excessively long residence time as compared with the heat stability of the polycondensate.

It is easier from the standpoint of operation to mix the final polycondensates or intermediate products after withdrawal and solidification, but this tends to cause separation among the components at the time of re-melting, bringing about fluc tuations in the mixing ratios. Moreover, it leads to a bad spinning condition and adversely affects the properties of the resulting filaments.

According to the present invention, such disadvantages can be avoided. The spinning can be carried out in a better condition than in the case of using polycondensates of different viscosities prepared from separate polycondensation reaction systems which have the same viscosity ranges as used in the present invention. Hence, it is possible to draw the filaments at a large draw ratio and obtain the filaments having great strength and having excellent crimp fastness. Of course, both the spinning and drawing can be effected under conditions than when using polycondensates obtained by a batchwise polycondensation.

The so prepared'mixture of the polycondensates can be immediately fed to a spinning apparatus, and subjected to conju- .gate-spinning. If desired, it is possible to make the mixture into granules, melt them, and then subject them to conjugatespinning. From the viewpoint of the cost of production, the former procedure is more advantageous. But when it is necessary to change the kind and combination of the components very often, or when the polycondensation reaction vessel is relatively small in size, it is convenient to use the mixture in the form of granules. For ease of operation of the polycondensation reaction vessel, it is best to follow the latter procedure.

It is known that generally composite fibers having an eccentric structure have an excellent crimpability, and a crimp development treatment will give fibers having excellent properties. The crimps of such filaments are similar to those of wool and are very stable. However, if used as multilament yarn, crimps appear as masses at the time of crimp-developing treatment since the quality of the filaments is very uniform. This brings about a yarn having a form similar to a knitted article when deknitted, and consequently having poor bulk.

For removing these defects and giving a strong ability to develop crimps of a larger number, it is advisable in this invention to use a spinneret in which the cross sectional area of one spinning orifice is 0.33 28 mm, preferably 0.4 10 mm, particularly preferably 1.0 7.0 mm*.

Usually, when composite multifilaments are subjected to crimp developing treatment, the development of crimps of each filament is restricted by adjoining filaments, and the number of resulting crimps becomes one-half one-fifteenth of that of the crimps obtained in the case of a composite monofilament. Thus, it is difficult to obtain excellent filaments wherein the number of crimps is at least 15, preferably at least 20, particularly preferably at least 25 per 25 mm of the filament length. By the use of the spinneret according to the invention, however, it is possible to overcome this difficulty.

We have found that with respect to the composite filaments or yarns of the invention, the number of crimps increases rapidly and the crimps make the filaments or yams thick and bulky if the cross sectional area of one spinning orifice is 0.33 to 0.4 mm, while there is no appreciable difference if the area is less than 0.33 mm*. It has also been found that this tendency ceases to exist if the area is within the range of 0.6 1.0 mm and best results are obtained if the area is 1.0 7.0 mm; that if the area exceeds 10 mm*, the drafting of a filament composed of two components tends to become non-uniform and the conjugate ratio tends to fluctuate in the lengthwise direction of the filament, resulting in a bad spinning condition and a bad crimpability; and that if the area exceeds 28 mm the results are infeasible.

A cross sectional area of the spinning orifice may be chosen according to its cross sectional configuration. For instance, if a nozzle hole is of circular cross section, a spinning orifice having a diameter of 0.65 5.5 mm can be used. But it should preferably have a diameter of 0.9 3.5 mm, more preferably 1.2 2.5 mm. On the other hand, it is preferable that the length of the spinning orifice be at Ieast0.5 times its diameter. The use of a spinning orifice having a length at least 3.5 times its diameter is particularly preferable to stabilize the spinning condition.

The nozzle hole may be of various shapes known in the art. For instance, the shape may be a circle, hexagon, polygon (having less than six angles), a straight line slit, and a curved slit. The nozzle hole shape also includes combinations of two or more of the same shapes or combinations of two or more different shapes. Preferably, the shape is such that the diameter of a circle circumscribing the above-mentioned figures does not exceed 10 mm. As the nozzle hole shape, a flat narrow shape is not preferable from the standpoint of uniformity of the resulting filaments. Let us suppose that an outlet of a spinning orifice constitutes a certain figure. Then, it is preferable that a ratio of the maximum to minimum widths of the figure should not exceed 20:1. The most preferable shape is a radical shape extending from a point or a central area having a certain size. Next comes a circular or polygonal shape in which a difference between its maximum and minimum widths is small. Incidentally, the maximum and minimum widths of a figure, as referred to herein, relate to the shape of its outer periphery. They does not refer to the shape of the respective slit when the figure consists of several slits. For instance, in the case of a spinning orifice composed of a slit having the form of a segment of a circle (larger than a semi-circle), its maximum width is the diameter of a circle circumscribing it, and the minimum width is the shortest distance between the chord and a point on the orifice which is farthest from the chord.

Spinning, drawing, and crimp developing operations for composite filaments or yarns are known per se, and a detailed description of them will be omitted in this specification. The spun filaments are made into filaments having crimpability by drawing in a customary manner. Usually, drawn filaments have some crimps. By heat-treating or swelling them in a relaxed condition, the latent crimps are developed and filaments having excellent crimps can be obtained.

The so crimped filaments can be used directly or after twisting or other treatment. Sometimes, the stretch or bulkiness of the filaments owing to crimping constitutes disadvantages in processing them at a high speed. In such a case, the crimped filaments can again be drawn to render a part of the crimps latent. For rendering the crimps latent, it is also effective to wind up the filament onto a bobbin under a high tension. But the most effective way is to hot-draw the filaments at a temperature lower than the point at which the filaments have previously been treated under relaxation. The crimps rendered latent after development in the above-mentioned manner have a larger capability of being developed than those before treatment under relaxation, and appear as excellent, fine crimps even under a considerably large restraining force. The effect of this treatment of rendering the crimps latent is especially conspicuous in the bulkiness of a fabric obtained by treatment under relaxation of the fabric after the weaving or knitting operation. This treatment is effective for the production of spun yarns from the crimped filaments of the invention.

As already mentioned hereinbefore, any fiber-forming polymer capable of forming a composite filament or yarn can be used as component (B). It is however preferable to use as component (B) a polymer having an intrinsic viscosity [1 different from that of component (A) which is withdrawn from the polycondensation reaction products used to form the mixtures (i) or (ii) mentioned before. Thus, by using only one multi-step continuous polycondensation reaction apparatus, composite filaments or yarns having an excellent quality can be obtained with good reproducibility of the quality and with simple operations.

The combinations of component (A) and component (B) may include a case where component (B) consists of the same mixture as the mixture used as component (A) having a different mixing ratio (see FIGS. 1 and 4), a case where component (B) is the same mixture as component (A) but at least one intermediate product contained therein has a different viscosity [1 from that of the intermediate product contained in component (A) (see FIGS. 2, 3 and 5), and a case where component (B) consists of the same end product as in component (A) (see FIGS. 1 This will be described with reference to the accompanying drawings.

FIGS. I 3 and FIGS. 6 8 are a flow sheet showing the production of composite filaments of polyethylene terephthalate according to the process of the invention.

FIGS. 4, 5, 9 and 10 are a flowsheet showing the production of composite filaments of a polyamide according to the process ofthe invention.

Referring to FIG. I, dimethyl terephthalate is put into a stock tank 1, and then fed into a melting device 2 where it is melted and heated to a predetermined temperature. Ethylene glycol (EG for short) is delivered to a mixer 3 where it is mixed with a catalyst and heated to a predetermined temperature. These two liquids are fed into an ester-interchange reaction vessel 4 and throughly mixed, and the ester-interchange reaction is initiated. A condenser 10 is provided to prevent loss of the starting materials owing to the sublimation of the .dimethyl terephthalate and the evaporation of ethylene glycol. The condenser 10 is adapted to reflux the products from the ester-interchange vessel 4 except methanol. An initial reaction liquid which is obtained when the ester-interchange reaction has proceeded to some extent enters an ester-interchange reaction vessel 5 where a thorough stirring is carried out and methanol is sufficiently removed by distillation. An ester-interchange reaction product of a high degree of ester-interchange is obtained here. This product consists predominantly of an initial condensate having an extremely low degree of polymerization. The formed methanol is taken out of the system through a condenser 11, and ethylene glycol is refluxed. The ester-interchange reaction product, together with an excess of ethylene glycol, is fed to a pre-polycondensation reaction 6. The ester-interchange is carried out nearly at atmospheric pressure, but the polycondensation is effected in vacuo. The pre-polycondensation reactor 6 is a reactor provided with a stirrer, and is adapted to carry out the reaction under reduced pressure at a temperature above the melting point of the polyester and to strip excess ethylene glycol. The intrinsic viscosity [1 of the obtained polycondensate is, for instance, 0.1 to 0.4 measured in an equal ratio ph'enol/tetrachloroethane mixture at 30 C. The obtained prepolycondensate is divided into three parts. One part is delivered to a final polycondensation reactor 7, and the other two parts are supplied respectively to a mixer 8 and a mixer 9. The final polycondensation reactor 7 is a reactor provided with a stirrer, and adapted to carry out the reaction in vacuo at a temperature above the melting point of the polyester. The intrinsic viscosity [1;] of the obtained final polycondensate is, for instance, 0.4 to 0.9. The product leaving this polycondensation reactor is divided into two parts, and supplied to the mixers 8 and 9. By mixing them at different ratios in these two mixers, two mixtures are prepared (in the drawings, the two mixtures are designated as polyester A and polyester B; A means component A, and B means component B). As the intermediate products to be mixed, the products from the esterinterchange vessel 5 can be used instead of the polycondensates from the pre-polycondensation reactor 6. It is also possible to mix both of them with the final polycondensate. If the desired low viscosity components have a viscosity lower than the products from the pre-polycondensation reactor 6, the mixing of the final polycondensate can be omitted. The residence time in the mixers 8 and 9 is within 30 minutes, preferably within 15 minutes. Too long a mixing time will cause undesirable discoloration or generation of a gas by decomposition.

FIG. 1 shows a process in which the ester-interchange process is used, but it is possible to replace the ester-interchange process by the direct esterification of terephthalic acid and ethylene glycol. Furthermore, the catalyst may be added by another method.

FIG. 2 shows the production of composite filaments of polyethylene terephthalate in which the ester-interchange reaction is carried out in a single step using a column. Referring to FIG. 2, the reference numerals are the same as those used in FIG. 1, and almost the same conditions as in FIG. 1 are used. An ester-interchange reaction column 4 is operated nearly at atmospheric pressure. The column may be a plate column or a packed tower. It is preferable to carry out the reaction with stirring. The introduction of ethylene glycol into the ester-interchange reaction column is made from the top of the column, but it may also be made from the bottom. The reference numeral 10 designates a rectifying device for the formed methanol and serves to return the entrained ethylene glycol to the reaction column.

The withdrawal and mixing of the polycondensates are substantially the same as those shown in FIG. 1. The difference is that in this example, a mixture of the final polycondensate and the ester-interchange reaction product is used as polyester A.

FIG. 3 shows the production of composite filaments of polyethylene terephthalate which is practiced by using four columns.

The ester-interchange reaction column 4 is, like in FIG. 2, a plate column or a packed tower. The reference numeral 5 represents a column for removing ethylene glycol, which is adapted to remove the excess ethylene glycol used in the ester-interchange reaction, under reduced pressure. The operation is performed under reduced pressure at a temperature above the melting point of the polycondensate having a low degree of polymerization, and there is obtained a polycondensate having a low degree of polymerization with an intrinsic viscosity [17] of less than 0.25, for'example. The prepolycondensation column 6 and the final polycondensation column 7 are wetted-wall towers provided with a stirrer, and are operated in vacuo at a temperature above the melting point of the polyester. The intrinsic viscosity [1 of the obtained polycondensate is 0.33 0.70 for the precondensate and 0.55 1.10 for the final polycondensation.

The reference numerals designate the same parts as in FIG. 1. The withdrawal and mixing of the polycondensates are effected on the same principle as in FIG. 1. FIG. 3, however, shows a case where ester-interchange reaction products are mixed because the product from the prepolycondensation column 6 has a viscosity higher than that of a low viscosity component of the composite filament.

The apparatus shown in FIGS. 1 to 3 can be used for the production of polyamides from nylon salts or for the production of polyureas from diamines and urea by making some changes in the operation conditions.

FIG. 4 shows the production of composite filaments of a polyamide from a nylon salt.

An aqueous solution of a nylon salt (a 1:1 salt of a dicarboxylic acid and a diamine) was prepared in dissolving device 1, and a stabilizer is added thereto. The solution is introduced into an evaporator 2, and heated under pressure to increase its concentration. The solution is then fed into a pre-condensation column 3 and some degree of polycondensation and dehydration are performed at a temperature above 200 C. and at a pressure of several atmospheres to 20 atmospheres or more. An aqueous solution of the obtained polycondenssate having a low molecular weight is passed to an evaporator 4 where it is dehydrated under atmospheric pressure or elevated pressure. The evaporator 4 shown in FIG. 4 is of a serpentineshape, but a wetted-wall tower or a tank provided with a stirrer can also be used for this purpose as it is only necessary to prevent the resulting polycondensates from freezing owing to a temperature drop. The lower molecular weight polycondensate from the evaporator 4 is fed into a final polycondensation reactor 5 and mixers 6 and 7. The final polycondensation reactor 5 is a vacuum reactor provided with a stirrer, in which the polycondensation reaction is performed, for instance, at a temperature of 260 310 C. and at a pressure of 0.1 mm Hg to normal atmospheric pressure. The polycondensate from the final polycondensation reactor 5 is divided into two parts, and fed into the mixers 6 and 7. These two parts are mixed at each of the mixers at different ratios to form two mixtures (designated as polyamide A and polyamide B).

The reference numeral 8 represents a condenser for the formed water, which actually acts as a heat-exchanger and is used to keep the heat of the pipe or evaporation of a solution of the nylon salt. The condensed water is used as a material water. The reference numeral 9 also designates a condenser for the formed water, which actually acts as a heat-exchanger. The condenser 9 is used to keep the heat of the pipe having a lower temperature and the dissolving of the nylon salt because the inside of the condenser 9 is maintained at a pressure lower than that of steam from the precondensation column 3. The reference numeral 10 designates a vacuum condenser having a special structure which is favorable for the removal of the high-melting low molecular weight polycondensate sublimated there.

The equipment shown in FIG. 4 can be applied to the production of a polyamide from omega-aminocarboxylic acid or lactam by making some changes in the operatingconditions.

FIG. 5 shows an example of producing composite filaments of a polyamide from epsion-caprolactam using a VK tube.

Episilon-caprolactam is fed into a dissolving device 1 and melted there. It is introduced into a mixer 2 where it is mixed with water, stabilizer, etc. The mixture is passed onto a towertype reactor 3 having rectifying plates therein but without a stirrer. While sending it in a piston-flow fashion, the temperature is raised to effect the ring-opening and polycondensation of the lactam (this tower-type reactor is usually called a VK tube). The obtained polycondensate contains great amounts of caprolactam and low molecular weight polycondensate, which are removed by means of a vacuum evaporator. The vacuum evaporator 4 is adapted to treat the polycondensate in a film or filament form at a temperature of 250 350 C. for instance and at a pressure of 0.05 5 mm Hg, for instance to remove its volatile component. Stirring may or may not be carried out.

The obtained polycondensate is continuously mixed in the mixer 6 with an intermediate product taken out before the vacuum evaporator 4. On the other hand, the polycondensate is mixed continuously in the mixer 5 with an intermediate product taken from the towertype reactor 3. These mixtures are used as components of the composite filaments (to be referred to as polyamide A and polyamide B in the drawing). The withdrawal and combination of the intermediate products need not be the same as those shown in Table 5. For instance, two mixtures of the former type having different mixing ratios are prepared and mixed with each other.

The tower-type reactor 3 may be divided into two or more, since it usually is of a considerable length. It may be used in a form bended in a V or N shape. It is also possible to effect the ring-opening of the lactam by reaction with water in an early stage of the reaction under high pressure. The reference numeral 7 represents a vacuum condenser. The volatile component condensed in the vacuum condenser 7 is again used as the starting material after such treatment as decomposition and refining.

FIGS. 6 to 10 show examples in which the final polycondensate from the same polycondensation system is used as component (B).

FIG. 6 is a flowsheet showing one example of the production of polyethylene terephthalate composite filaments.

Dimethyl terephthalate is put into a stock tank 1, and fed into a melting device 2 where it is heated to a predetermined temperature. Ethylene glycol (EG for short) is delivered to a mixer 3 where it is mixed with a catalyst and heated to a predetermined temperature. The two liquids are fed into a preester-interchange reaction vessel 4, and well mixed. The ester-interchange reaction is initiated. A condenser 10 is provided to prevent the loss of materials owing to the sublimation of dimethyl terephthalate and the evaporation of ethylene glycol. The condenser 10 is adapted to reflux the products coming from the preester-interchange vessel 4 except methanol. An initial reaction liquid obtained when the esterinterchange reaction has proceeded to some extent enters as ester-interchange vessel 5, where a thorough stirring is performed and methanol is sufficiently removed. Thus, an esterinterchange reaction product having a high degree of ester-interchange is obtained. The product consists predominantly of an initial polycondensate having a very low degree of polymerization. The formed methanol is taken out of the system through a condenser 11, and ethylene glycol is refluxed. The ester-interchange reaction product is supplied to a prepolycondensation reactor 6 together with excess ethylene glycol. The ester-interchange reaction is carried out at atmospheric pressure, but the polycondensation is carried out in vacuo. The prepolycondensation reactor 6 is a reactor provided with a stirrer and is adapted to perform the reaction at high temperatures under reduced pressure, and at the same time strip excess ethylene glycol. The intrinsic viscosity of the obtained prepolycondensate is, for instance, 0.1 to 0.4 measured in an equal ratio phenol/tetrachloroethane mixture at 30 C. The prepolycondensate is divided into two parts. A larger part is fed into a final polycondensation reactor 7, and the remaining part is fed into a mixer 8. The final polycondensation reactor is a reactor provided with a stirrer, and adapted to perform the reaction in vacuo at a temperature above the melting point of the polyester. The intrinsic viscosity of the obtained final polycondensate is, for instance, 0.4 0.9. A part of the final polycondensate is fed into the mixer 8, and the remainder is used as component (B) of the composite filaments (designated as polyester B in the drawing). The prepolycondensate from the prepolycondensation reactor 6 and the final polycondensate from the final polycondensation reactor 7 are thoroughly mixed with each other, and the mixture is used as component (A) of the composite filaments (designated as polyester A in the drawings). It is possible to use the ester-interchange reaction product from the ester-interchange reaction vessel 5 instead of the intermediate product from the prepolycondensation reactor 6. Or they may be used in admixture with the final polycondensation product. If the intermediate product from the precondensation reactor 6 has a lower viscosity than that of the desired low viscosity product, the mixing of the final polycondensate can be omitted. The residence time in the mixer 8 is within 30 minutes, preferably within minutes. Too long a mixing time will cause undesirable discoloration or generation of a gas by heat decomposition.

FIG. 6 shows the case of using an ester-interchange process. It is possible to replace the ester-interchange process by a direct esterification of terephthalic acid and ethylene glycol. Furthermore, it is permissible to use another method in adding a catalyst.

FIG. 7 shows an example of producing composite filaments of polyethylene terephthalate like FIG. 6 in which the ester-interchange reaction is performed in a single step. The reference numerals are the same as those used in FIG. 6, and the conditions used are also the same. The ester-interchange reaction column 4 is operated nearly at atmospheric pressure.

The reference numeral 10 is a rectifying device for the formed methanol and serves to return the entrained ethylene glycol to the reactor. The reference numeral 12 designates a vacuum condenser.

With regard to the withdrawal of the polycondensation product, the example of FIG. 7 is quite the same as that of FIG. 6.

FIG. 8 shows an example of the production of composite filaments of polyethylene terephthalate, as in the case of FIGS. 6 and 7, using four columns. The reference numeral 4 designates an ester-interchange reaction column of the type same as in FIG. 7. The reference numeral 5 designates a column for removing ethylene glycol where excess ethylene glycol used in the ester-interchange reaction is removed under reduced pressure. Both the precondensation reactor 6 and final polycondensation reactor are wetted-wall towers having a stirring device, and are operated at a temperature above the melting point of the polyester. The intrinsic viscosity [1;] of the polycondensate is for instance, 0.35 0.65 for the prepolycondensate, and for instance 0.55 1.10 for the final polycondensate.

Other reference numerals designate the same parts as in FIG. 6. The withdrawal and mixing of the polycondensates are performed on the same principle as in FIG. 6. FIG. 8 however shows a case where the viscosity of the product from the prepolycondensation reactor is higher than the desired viscosity of the low viscosity component.

The apparatus shown in FIGS. 6 to 8 can be applied to the production of polyamides from nylon salts or the production of polyureas from diamines and urea by changing the operating conditions.

FIG. 9 shows an example of producing composite filaments of a polyamide from a nylon salt.

An aqueous solution of a 1:1 nylon salt of a dicarboxylic acid and a diamine is prepared in a dissolving device 1, and a stabilizer is added. The solution is delivered to an evaporator 2 and heated under pressure to increase the concentration. It is fed into a prepolycondensation reactor 3, and polycondensed to some degree at a temperature above 200 C. and at a pressure from several atmospheres to atmospheres or higher.

An aqueous solution of the low molecular weight polycondensate obtained is fed into an evaporator 4, and dehydrated at atmospheric or elevated pressure. The evaporator 4 shown in FIG. 9 is of a serpentine-shape, but a wetted-well tower or a tank provided with a stirrer can also be used for this .purpose as it is only necessary to prevent the resulting polycondensates from freezing owing to a temperature drop. The low molecular weight polycondensation product from the evaporator 4 is fed to the final polycondensation reactor 5 and the mixer 6. The latter is mixed with the polycondensate from the final polycondensation reactor 5 to form a low viscosity component (polyamide A in the drawing). The final polycondensation reactor is a vacuum reactor provided with a stirrer which is adapted to perform the polycondensation at 260 310 C. and at 0.1 mm Hg to normal atmospheric pressure.

The reference numeral 8 designates a condenser for the formed water, but it actually serves as a heat-exchanger to be used for keeping the heat of the pipe or evaporating of the nylon salt solution. The condensed water is used as a material water. The reference numeral 9 also is a condenser for the formed water, but it actually acts as a heat-exchanger. Since the inside of the condenser 9 is maintained at a pressure lower than that of steam coming from the tower 3, it is used for keeping the heat of the pipe at lower temperatures and for dissolving the nylon salt. The reference numeral 10 designates a vacuum condenser which has a special structure which is favorable to the continuous removal of the high-melting lowmolecular-weight polycondensates sublimated therein.

The equipment of FIG. 9 can be applied to the production of polyamide from omega-aminocarboxylic acid or lactam by changing the operation conditions to some extent.

FIG. 10 shows an example of producing composite filaments of a polyamide from epsilon-caprolactam using a VK tube.

Epsilon-caprolactam is fed into a dissolving device 1 and melted there. It is introduced into a mixer 2 where it is mixed with water, stabilizer, etc. The obtained mixture is passed onto a tower-type reactor 3 having rectifying plates therein but without a stirrer. While sending it in a piston-flowfashion, the temperature is raised to effect the ring-opening and polycondensation of the lactam (this tower-type reactor is usually called a VK tube). The obtained polycondensate contains great amounts of caprolactam and low-molecular-weight polycondensate, which are removed by means of a vacuum evaporator 4. The vacuum evaporator 4 is adapted to treat the polycondensate in a film or filament form at a temperature of 250 350 C., for instance and at a pressure of 0.05 5 mm Hg, for instance to remove its volatile component. Stirring may or may not be carried out.

The obtained polycondensate is used as component (B) of the composite filaments (designated as polyamide B in the drawing). Component (A) is prepared by continuously mixing the products taken out before or after the vacuum evaporator 4 or from the tower type reactor 3 in the mixer 5 (designated as polyamide A in the drawing). The withdrawal of the intermediate products may be effected in a different manner from that shown in Table 10. For instance, an intermediate product taken out before the vacuum evaporator 4 may be mixed with an intermediate product taken out from the tower-type reac- 01.

The tower-type reactor 3 may be divided into two or more sections, since it usually is of a considerable length. It may be used in a form bended in a V or N shape. The volatile component condensed in the vacuum evaporator 7 is again used as the starting material after such treatment as decomposition and refining.

In the above-given ten embodiments, description has been made with respect to polycondensates exclusive of copolycondensates. It is to be understood however that the present invention is applicable to copolycondensates of the above-mentioned polycondensates with other cocondensable substances of minor amounts. It is further possible to add, to the polycondensates, catalysts, promotors, pigments, dyestuffs, optical brightening agents, anti-oxidants, ultraviolet ray absorbents, antistatic agents, and various stabilizers. The addition of these compounds is effected atpositions most suitable according to the purpose and effect of addition.

In the foregoing description, we have directed out explanation to bi-component composite filaments. The invention can however be applied with good results to composite filaments obtained from three or more components. In the case of ternary component composite filaments, polycondensates prepared in separate polycondensation vessels or dissimilar polymers can be used.

This invention will be hereinafter detailed by referring to examples, but it is not limited by these examples.

i A continuous polycondensation apparatus comprising a plurality of reactors successively connected one by one and having different vconfigurations according to the degree of polycondensation was used. Polyethylene terephthalate of [1 0.59 taken from a final reactor was used as component (B). A composition of [1;] 0.39 prepared by mixing continuously equal amounts of the above polyethylene terephthalate of [1 0.59 and polyethylene terephthalate of [1; 0.19 taken from an intermediate reactor was used as component (A). The composite spinning was continuously conducted with the use of above components (A) and (B) to obtain a composite yarn of 48 filaments (the monofilament size being 7.0 denier in, which both components were bonded to each other in the bimetal form. The spinning nozzle diameter of the spinneret used was 0.6 mm and the wind-up rate of the spun yarn was 900 m/min.

ii Two classes of polyethylene terephthalate of [1;] 0.78 and [1 0. I were prepared by employing the same continuous polycondensation apparatus as used in above Example 1( i Two compositions having the same viscosities as those of components (A) and (B) of Example l(i), respectively, were prepared by mixing continuously above two classes of polyethylene terephthalate at different mixing ratios. The composite spinning was continuously conducted under the same conditions as in Example 1-( i) with the use of above two compositions.

The measurement of the viscosity was made based on the pressure lowering at a portion, corresponding to the reactor from which the polymer was taken, of a tube extending from the mixer to the spinning machine and having a uniform configuration throughout its entire extension.

For comparisons sake, the following two experiments were conducted.

Two polycondensation apparatuses were used instead of the polycondensation apparatus used in Example 1. Polyethylene terephthalate having the same viscosity as that of component (B) in Example l(i) was prepared by employing one of the two polycondensation apparatus. Polyethylene terephthalate having the same viscosity as that of component (A) in Example l(i) and prepared by employing the other polycondensation apparatus was used instead of the mixture of two classes .of polyethylene terephthalate from the same polycondensation system, which was used as component (A) in Example l(i). The composite spinning was conducted in the same manner as in Example 1 by employing the above two classes of polyethylene terephthalate prepared from a different polycondensation system to obtain a composite yarn. The adjustment of the viscosity was conducted in the same manner as in Example 1( ii). (Comparative Example 1) Polyethylene terephthalate of [1 0.59 was prepared by employing a continuous polycondensation apparatus, a part of which was transferred to a storage tank and was binned until the viscosity was lowered to that of component (A) in Example l(i). The composite spinning was conducted in the same manner as in Example 1, with the use of above polyethylene terephthalate of [1;] 0.59 and that whose viscosity had been reduced by binning. The adjustment of the viscosity was conducted in the same manner as in Example l(ii).

The Tesults of Example 1 and Comparative Examples 1 and 2 are shown in Table I below. The values of yam breakage during spinning," number of deep dyeing defects", bulk density after development of crimps" and natural draw ratio in Table l were measured as follows.

YARN BREAKAGE DURING SPINNING The number of breakages in the monofilament or yarn (the number of broken yarn or monofilaments wound on a godet roller) was actually counted and the value was expressed in NUMBER OF DEEP DYEING DEFECTS A sufiicient number of monofilaments to give a drawn yarn of 150 200 denier were drawn into a yarn (the doubling was conducted if necessary) and the yarn was twisted at 30 50 turns/m, followed by reeling. The reeled yarn was freely shrunk in boiling water and then dyed. The dyed yam was knitted into a plain fabric where the loop density was 200 '250 loops/cm, and the number of deeply-dyed defects on the fabric was counted. The value of "number of deep dyeing defects" was expressed in terms of the number of defects per kg of they fiber. The dyeing was conducted for 60 minutes in a water bath containing 0.2 percent by weight based on the fiber of Eastman Polyester Red B (product of Eastman Kodak Co.) and maintained at 105 C., the bath ratio being 1:50. The smaller value of number of deep dyeing defects" a fiber exhibits, the more excellent it is.

BULK DENSITY AFTER DEVELOPMENT OF CRIMPS In case the crimp-development is conducted on a knitted fabric, the bulkiness of the fabric is greatly influenced by crimpability of the fiber. Accordingly, the test was conducted on a plain knitted fabric having a loop density of 20 i 2 loops/cm*, prepared from a yarn of 1,000 1- 50 denier which had been twisted at 30 turns/m. The crimp development was conducted by free shrinkage in boiling water. The bulk density was measured on the fabric made bulky by the crimp development, under a load of 25 g/cm". In case a fabric exhibits a bulk density of above 0.2, it means that the fiber is insufficient in crimpability. The smaller is the value of bulk density after development of crimps, the more excellent the fiber is.

NATURAL DRAW RATIO In fibers spun under substantially the same conditions, the value of natural draw ratio" can be a criterion for appreciat ing the uniformity in spinning. In case the spinning is smoothly performed and a uniformlyspun fiber is obtained, the fiber exhibits a high value of "natural draw ratio." Accordingly, the higher value natural draw ratio a fiber exhibits, the more excellent it is.

Natural draw ration" was defined as the maximum draw ratio at which a continuous drawing could be conducted for more than 3 minutes without breakage of monofilaments. The sample fiber was continuously drawn in hot water of C. between two sets of rolls having different peripherical speeds while the take-up speed after drawing was maintained at 50 m/min. M

TABLE I Yarn break- I age during Number of Bulk density spinning deep dyeing after de- Natural (MW/Mn) (breakuges/ defects vclopn ent draw cal Mw/Mu kg.) (defects/kg.) 0i crimp ratio i l l If): '1. t l 05 l (m I igiviscosi ycompmum L. 5.. I L L 3 Low viscosity componvui, 11; -=U.3'.l 3. 51 3.14 l 0 l 51 I lcmllllmm I n: 1 l H l 1 l l0 18 I lgli viscosity compnncu 1; 4.)! i.- L. L H 3.5 lmw viscosity cmnponcnl In] (LBJ 1;. 7-1 5.30 l H (-om mrnlivu l'lxnmplc 1:

.l igh viscosity conlpmmnt, |1 ]--'(l.5!l 2.00 2.05 l 21 L, L 24 3:: Low viscosity cmnpmicnt, In] =0.3l nu... l 2.00 1.95 l

Table 1- Continued Yarn breakage during Number of Bulk density spinning deep dyeing after de- Natural (Mw/Mn) (breakagos/ defects velopment draw eal. Mw/Mn 100 kg.) (defects/kg.) oi crimp ratio 1 2.00 1.88 y component, [1;l=0.3!l 6 2.00 2.41 86 55 26 0 I 'Iheoretiml values.

2 Mixture of equal amounts of polymers of l ]=5.9 and [1;l=0.19 from the same polymerization system as of high viscosity compullout.

Mixture of polymer of l1;]=0.78 and [1;] =0.15 prepared from the same polymerization system.

I Not mixture EXAMPLE 2 AND COMPARATIVE EXAMPLE 3 Two classes of polyhexamethylene adipamide of [n] 1.65- and [1;] 0.32 were prepared by employing one continuous polycondensation apparatus in the same manner as in Example l. (The value of viscosity [1;] was measured in metacresol maintained at 30 C.) Two composite spinning components were prepared by mixing continuously the above two classes of polyhexamethylene adipamide at ratios of 8:3 and 1:2, respectively. Then, the composite spinning was conducted by employing the above two mixtures as composite spinning components in the same manner as in Example 1. Results are shown in Table II below.

For comparisons sake, in Table II there are given the results of Comparative Example 3 which was conducted as follows.

Two composite spinning components having the same viscosities as those of the two components used in Example 2 were separately prepared by employing two different continuous polycondensation apparatuses. Each of the components was not a mixture but a unit polymer. The composite spinning was conducted in the same manner as in Example 2.

TAB LE II Comparative Example 2 Example 3 High Low High Low visvisvisviseosity eosity cosity eosity comcomcom component ponent ponont ponent (MW/Mn) cal 4. as 5.13 2. e0 2. 00' MW/Mn 4. 44 4. 87 2. 07 2. 17 Yarn breakage during spinning (breakages/IOO kg.) 0.26 0. 05 Number of deep dyeing defects (defects/kg.) 0. 67 3. 6 Bulk density after day ment of crim 0.14 0. 25 Natural draw ratio- 4. 1 3. 3

1 Theoretical values.

EXAMPLE 3 composite spinning machine, and each of the mixtures was ex-: truded from a spinning nozzle of 1.5 mm in diameter at a rate of 0.25 g/min. The extrudate was wound up at a rate of 900 m/min. The spinneret temperature was at 280 C. The extrudate was cooled by an air current of room temperature flowing horizontally at a rate of 0.3 m/sec in a zone ranging from 1 to 150cm below the spinneret.

The wound-up yarn was drawn at a draw ratio of 3.2 at two states by means of a hot pin maintained at 90 C. and a hot plate maintained at 140 C. Then, the yarn was twisted at turns/m and reeled. The reeled yarn was relaxed at 145 C. for

but polymer prepared from polymerization system diiferent from that of hi h viscosit com onent. 5 N ot mixture but product obtained by storing high viscosity component to reducing the v iscosity. y p

' 10 minutes. The resulting yarn had such excellent crimp pro- 5 perties as a number of crimp of 36.8 crimps/ZS mm, a rate of crimp of 47.3 percent and a recovery of crimp of 93.6 percent.

For comparisons sake, two classes of polyethylene terephthalate having melt viscosities [1 of 0.63 and 0.40, respectively, which were almost the same viscosities as those of the two components of the above composite fiber, were prepared separately, melted by means of an extruder and spun into a composite fiber under the same conditions as above. The resulting yam was not so different from the composite yarn of above Example 3 in crimp properties, but the fibers were very different from each other with respectv to yarn breakage during spinning. More specifically, in the composite fiber of the above comparative example the value of the yarn breakage during spinning was 2.1 breakages/IOO kg, whereas the composite fiber obtained in accordance with the process of this invention exhibited only 0.1 breakages/ 100 kg. Thus, it is seen that the composite fiber of this invention prepared by employing mixtures was superior to the composite fiber of the comparative example.

EXAMPLE 4 Crimp properties were examined with respect to fibers prepared by employing the same polyester as used in Example 3 and conducting the spinning, drawing and heating operations under the same conditions as in Example 3 except varying the diameter of the spinning nozzle.

In case the diameter of the spinning nozzle was 0.25 mm, the resulting fiber exhibited such inferior crimp properties as a number of crimp of 16.3 crimps/25 mm, a rate of crimp of 19.6 percent and a recovery of crimp of 95.2 percent. In the case of the spinning nozzle of 0.4 mm diameter, crimp properties of the resulting fiber were similar to those of the above fiber, while the fiber prepared by employing a spinneret of a nozzle diameter of 0.7 mm exhibited somewhat improved crimp properties. In case the diameter of the spinning nozzle was either 1.0 mm, 2.0 mm or 2.5 mm, the resulting fiber possessed excellent crimp properties equivalent to those of the fibers obtained in Example 3. In case the diameter of the spinning nozzle exceeded 3.0 mm, a tendency that the crimp distribution in the longitudinal direction became somewhat non-uniform was observed and the spinning stability was somewhat reduced. In case the diameter of the spinning nozzle exceeded 6 mm, the spinning condition went down extremely. Accordingly, it was judged that the use of such great spinning nozzle would not be of any practical value.

EXAMPLE 5 The polycondensation apparatus illustrated in FIG. 2 was employed instead of the polymerization apparatus shown in FIG. 1, and Example 3 was repeated. The spinning could be conducted smoothly and a polyethylene terephthalate composite fiber having similarly excellent crimp properties was obtained.

EXAMPLE 6 Polyethylene terephthalate was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 3, and a composite fiber was prepared therefrom Two mixtures of equal amounts were prepared by mixing polyethylene terephthalate of [1 0.73 taken at a rate of 9 kg/hr from final polycondensation column 7, polyethylene terephthalate of [1;] 0.45 taken at a rate of 1 1.25 kg/hr from pre-polycondensation column 6 and polyethylene terephthalate of [1 0.13 taken at a rate of 3.75 kg/hr from ethylene glycol removal column 5, at mixing ratios of 3: 1 and 0:1 1:5, respectively. The values of WW1 of the mixtures were 3.09 and 2.75, respectively. Each of the mixtures was extruded at a rate of 1 g/min from a spinning nozzle ofa 1.2 mm diameter in a manner such that both components would be arranged parallelly and eccentrically. The extrudate was wound up at a rate of 900 m/min. The wound-up fiber was drawn at a draw ratio of 2.9 by means of a hot pin maintained at 100 C. and a hot plate maintained at 160 C. Then, the drawn fiber was continuously shrunk at the relaxed state in hot air maintained at 200 C., and wound up at a speed 55 percent as high as the drawing speed. The resulting fiber possessed crimp properties: a number of crimp of 28.5 crimps/25 mm, a rate of crimp of 35.8 percent and a recovery of crimp 96.2 percent.

EXAMPLE 7 Polyhexamethyleneadipamide was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 4, and a composite fiber was spun therefrom.

Equal amounts of two mixtures were prepared by mixing polyamide of [1;] 1.52, measured in metacresol at 30 C., taken at a rate of 4.6 kg/hr from final polycondensation reactor and polyamide of [1 0.29 taken at a rate of 3.8 kg/hr from evaporator (4), at mixing ratios of 23:9 and 3:5, respectively. The AW/17in values of the mixtures were 3.76 and 9.27, respectively.

Each of the mixtures was extruded at a rate of 0.5 g/min from a spinning nozzle having a 2.0 mm diameter in a manner such that both components would be arranged parallelly and eccentrically. The extrudate was wound up at a rate of 1,150 m/min.

The resulting fiber was cold drawn at a draw ratio of 2.8 and relaxed at 175 C. for 2 minutes. As a result, there was obtained a crimped fiber having crimp properties: a number of crimp of 21.8 crimps/25 mm, a rate of crimp of 38.3 percent and a recovery of crimp of 97.3 percent.

EXAMPLE 8 Poly-epsilon-capramide was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 5, and a composite fiber was spun therefrom.

Equal amounts of mixtures were prepared by mixing polyamide [1;] 1.87, measured in metacresol at 30 C., taken at a rate of 3.75 kg/hr from vacuum evaporator 4 and polyamide of [1 0.17 taken at a rate of 2.25 kg/hr from the midway of polycondensation column 3 at mixing ratios of 3:1 and 1:1, 60

respectively. The WAT/1Y1 values of the mixtures were 2.78

and 3.59, respectively.

EXAMPLE 9 Polyethylene terephthalate was prepared by polycondensation employing the apparatus illustrated in FIG. 6, and a composite fiber was prepared therefrom.

Polyethylene terephthalate of [7;] 0.63 was taken at a rate of 22.5 kg/hr from final polycondensation reactor 7, and a part of the above polyethylene terephthalate corresponding to a portion taken at a rate of 7.5 kg/hr was continuously mixed with polyethylene terephthalate of [17] 0.17 taken at a rate of 7.5 kg/hr from prepolycondensation reactor 6. The Mw/Mn value ofthe mixture was 3.28.

The resulting two condensates were fed to a composite spinning machine, and each of them was extruded from a spinning nozzle ofa 1.25 mm diameter at a rate of 0.25 g/min. The extrudate was wound up at a rate of 900 m/min. The cooling of the extrudate was effected by an air current flowing horizontally at a rate of 0.3 m/sec in a zone ranging from 1 to 150 cm below the spinneret. The wound-up fiber was drawn at a draw ratio of 3 at two stages by means of a hot pin maintained at C. and a hot plate maintained at C. Then, the fiber was twisted at 15 turns/m and reeled. The reeled fiber was subjected to a heat treatment at the relaxed state for 10 minutes at C. to obtain a crimped fiber having crimp properties: a number of crimp of 35.8 crimps/25 mm, a rate of crimp of 43.8 percent and a recovery of crimp of 93.4 percent.

For comparisons sake, polyethylene terephthalate (not a mixture) of the same viscosity ([1 0.41) as that of the low viscosity component of the above composite fiber was prepared separately, and this polyethylene terephthalate and the above polyethylene terephthalate of ['n] 0.63 were melted by means of an extruder and spun into a composite fiber. Although the resulting fiber exhibited similar crimp properties to those of the above fiber prepared in accordance with this invention, in the fiber of this comparative example the value of the yarn breakage during spinning was 2.3 breakages/ 100 kg, whereas in the fiber of this invention the value was only 0.2 breakage/100 kg. Thus, it is seen that the use of a mixture of at least two polycondensates of different viscosities as the low viscosity component of a composite fiber in accordance with this invention gives excellent results.

EXAMPLE 10 Example 9 was repeated by employing the polycondensation ap-paratus illustrated in FIG. 7 instead of the polycondensation apparatus shown in FIG. 6. The spinning could be performed smoothly, and a polyethylene terephthalate composite fiber excellent in crimp properties was obtained.

EXAMPLE 1 l Polyethylene terephthalate was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 8, and a composite fiber was prepared therefrom.

Polyethylene terephthalate of [1 0.78 taken at a rate of 12 kg/hr from final polycondensation column 7 was used as the high viscosity component. A mixture was prepared by mixing continuously polyethylene terephthalate of [n] 0.45 taken at a rate of 8.5 kg/hr from pre-polycondensation column 6 and polyethylene terephthalate of [1 0.13 taken at a rate of 3.5 kg/hr from ethylene glycol removal column 5, and this m ixtu r was used as the low viscosity component. The value of Mw/Mn of the mixture was 2.68.

By employing a Y-figured spinning nozzle, each branch of which had a width of 4 mm and a length of 12 mm and the sectional area of which was about 1.5 mm the above two components were composite spun in a manner such that they would be arranged parallelly and eccentrically. The spinneret 70 surface was maintained at a temperature of 286 C. The extrudate was wound up at a rate of 900 m/min.

The wound-up fiber was drawn at a draw ratio of 2.9 at two stages by means of a hot pin maintained at 100 C. and a hot plate maintained at C., and then shrunk continuously in the air of 200 C. at a shrink ratio of 45 percent to develop crimps in the fiber. The resulting fiber exhibited crimp properties: a number of crimp of 23.5 crimps/25 mm, a rate of crimp of 33.9 percent and a recovery of crimp of 96.2 percent.

A composite fiber having the same composition as above was prepared under the same cooling conditions as above by employing a Y-figured spinning nozzle having a similar configuration but a sectional area of 0.2 mm'. This fiber was inferior to the above-mentioned fiber with respect to number of crimp, rate of crimp, recovery of crimp and bulkiness. Further, the spinning could not be conducted as smoothly as in the above example.

EXAMPLE 12 Composite fibers were prepared from the same components as in Example 1 1 and under the same cooling-conditions as in Example 11, with the use of spinnerets of Y-figure spinning nozzles, sectional areas of which were approximately 0.047 mm (0.05 mm X 0.3 mm), approximately 0.19 mm (0.1 mm X 0.6 mm), approximately 0.25 mm (0.2 mm X 0.4 mm), approximately 0.36 mm (0.2 mm X 0.6 mm), approximately 0.51 mm (0.25 mm X 0.65 mm), approximately 0.66 mm (0.3 mm X 0.7 mm), approximately 1.04 mm (0.4 mm X 0.8 mm), approximately 2.28 mm (0.6 mm X 1.2 mm), approximately 4.44 mm (0.6 mm X 2.4 mm), approximately 6.60 mm (0.6 mm X 3.6 mm), approximately 12.1 mm 1.0 mm X 4.0 mm), approximately 27 mm" 1.5 mm X 6 mm; the diameter of the circumscribed circlebeing approximately 13.7 mm) and approximately 30 mm (2.5 mm X 4.0 mm), respectively.

The width and length of one branch of each spinning nozzle are shown in parentheses.

These fibers were drawn and relaxed under the same conditions as in Example 1 1 to develop crimps in the fibers.

When eight spinnerets having a spinning nozzle sectional area of from 0.36 mm to 12.1 mm were used, crimped fibers having good properties could be obtained. However, among them, only three spinnerets having spinning nozzle surface areas of 1.04 mm, 2.28 mm and 4.44 mm, respectively,

could give crimped fibers having extremely excellent proper-' ties comparable to those of the fiber obtained in Example 3. 40 Crimped fibers obtained by employing a spinneret having a spinning nozzle sectional area of 0.25 mm or less, or 27 mm:

or more were inferior in properties to the above eight fibers.

EXAMPLE 13 v W Crimped polyester fibers of the same composition as that of the fiber of Example 11 were prepared under the same cool ing, drawing and relaxing conditions as in Example 1 l, by employing various spinnerets of X-figured T-figured, L-figured, V-figured,#-figured,l -figured,]- -figured, l-l-figured, triangular, square, rectangular (longer side 1.5 3 X shorter side), pentagonal or hexagonal spinning nozzles, or spinnerets of spinning nozzles of a configuration where five branches of almost equal lengths were extended from the center with angles formed by every two neighboring branches being almost equal; and by varying the spinning nozzle sectional area with respect to each of above mentioned various types of spinnerets. A similar tendency as in Example 12 was observed with respect to each type of spinneret.

EXAMPLE l4 Polyhexamethylene adipamide was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 9, and a composite fiber was prepared therefrom.

Polyamide of [1;] 1.25, measured in matacresol at 30 C., was taken at a rate of 6.4 kg/hr from final polycondensation reactor 5. A part of the polyamide corresponding to a portion taken at a rate of 4.2 kg/hr was used as high viscosity component, and the remainder corresponding to a portion taken at a rate of 22 kg/hr was mixed with polyamide of [1;] 0.25

taken at a rate of 2 kg/hr from evaporator 4, and the mixture was used as low viscosity component. The value of W/m of t he mixture was 4.15.

Each of the above two components was extruded at arate of g/min from a spinning nozzle having a diameter of 2.0 mm I a crimped fiber having crimp properties: a number of crimp of i 21.8 crimps/25 mm, a rate of crimp of 38.3 percent and a recovery of 97.4 percent.

EXAMPLE 1s Poly-epsilon-caproamide was prepared by polycondensation employing the continuous polycondensation apparatus illustrated in FIG. 10.

Polyamide of [1 1.08, measured in metacresol at 30 C., was taken at a rate of 5 kg/hr from vacuum evaporator (4). A part corresponding to a portion taken at a rate of 3 kg/hr was used as the high viscosity component, and the remainder corresponding to a portion taken at a rate of 2 kg/hr was mixed with polyamide of [1;] 0.17 taken at a rate of 1 kg/hr from the midway of polycondensation column (3). The mixture was used as the low viscosity component. The value of lTv/m of the mixture was 6.39.

Each of the two components was extruded at a rate of 2.5

s jn in frprn a spinning nozzle of a 0.9 mm diameter in a manner such that both components would be arranged paral lelly and eccentrically. The extrudate was wound up at a rate of 1,075 m/min.

The resulting fiber was cold drawn at a draw ratio of 3.1 and relaxed at 160 C. for 3 minutes to obtain a crimped fiber having crimp properties: a number of crimp of 23.7 crimps/25 mm, a rate of crimp of 29.2 percent and a recovery of crimp of 92.9 percent.

What is claimed is:

1. In a process for the production of composite filaments and yarns comprising simultaneously melt-spinning at least two thermoplastic linear polycondensation reaction products having different melt viscosities, the improvement wherein said two thermoplastic linear polycondensation reaction products comprise f A. A first component comprising a mixture obtained by continuously mixing in the molten state i. a thermoplastic linear polycondensation reaction end product of a multi-step continuous polycondensation reaction and at least one thermoplastic polycondensation reaction intermediate product of the same continuous polycondensation reaction; or ii. at least two different thermoplastic polycondensation reaction intermediate products of the same continuous polycondensation reaction; said mix ture having a ratio W/m of more than 2.5, Mw

being the weight average molecular weight of said end product and intermediate product and M71 being the number average molecular weight of said end product and intermediate product; and

B. a second component comprising a thermoplastic linear polycondensation reaction product of the same continuous polycondensation reaction as in (A) having an intrinsic viscosity different from that of component (A). 2. The process of claim 1 wherein said melt-spinning is carried out using a spinning orifice having a cross sectional area ofO.33 to 28 mm 3. The process of claim 1 wherein said component (A) has an NEW/Mn ratio of not more than 10.

4. The process of claim 3 wherein said component (B) is the same mixture as component (A) having a different mixing ratio.

5. The process of claim 3 wherein said component (B) is the same mixture as component (A) but at least one intermediate ;product contained therein has a different viscosity from that f i of the intermediate product contained in component (A). 6. The process of claim 3 wherein said component (B) con- V sists of said end product contained in component (A).

7. The process of claim 1 wherein said linear condensation products are selected from the group consisting of linear polyamides, linear polyesters and linear polyureas. 

2. The process of claim 1 wherein said melt-spinning is carried out using a spinning orifice having a cross sectional area of 0.33 to 28 mm2.
 3. The process of claim 1 wherein said component (A) has an Mw/Mn ratio of not more than
 10. 4. The process of claim 3 wherein said component (B) is the same mixture as component (A) having a different mixing ratio.
 5. The process of claim 3 wherein said component (B) is the same mixture as component (A) but at least one intermediate product contained therein has a different viscosity from that of the intermediate product contained in component (A).
 6. The process of claim 3 wherein said component (B) consists of said end product contained in component (A).
 7. The process of claim 1 wherein said linear condensation products are selected from the group consisting of linear polyamides, linear polyesters and linear polyureas. 